The code in question is *only* relevant in non-`PRODUCTION` mode, i.e. the *development* version of the viewer run with `gulp server`, and has been completely unused at least since SystemJS was added.
I really cannot see any reason to keep this, since it's code which first of all isn't shipping and secondly isn't even being used in the development viewer.
When `ReadableStream` support was added to the `MessageHandler`, the `_onComObjOnMessage` function became more complex than previously.
All of the nested `if`/`else if`/`else` branches are now, at least in my opinion, making some of this code a bit difficult to follow. Hence this patch, which attempts to help readability by making use of early `return`s and `Error`s.
The patch also changes a couple of `var`/`let` occurences to `const`.
Note that using `in` leads to unnecessary stringification of the properties, which seems completely unnecessary here. To avoid future problems from these changes the `MessageHandler.on` method will now assert, in non-`PRODUCTION`/`TESTING` builds, that it's always called with a function as expected.
This patch also renames `callbacksCapabilities` to `callbackCapabilities`, note the removed "s", since using a double plural format looks a bit strange.
Given that the `isReply` property is an internal implementation detail, changing its type shouldn't be a problem. Note that by directly indicating if either data or an Error is sent, it's no longer necessary to use `in` when handling the callback.
Currently, for data in `ChunkedStream` instances, the `getMissingChunks` method is used in a couple of places to determine if data is already available or if it needs to be loaded.
When looking at how `ChunkedStream.getMissingChunks` is being used in the `ObjectLoader` you'll notice that we don't actually care about which *specific* chunks are missing, but rather only want essentially a yes/no answer to the "Is the data available?" question.
Furthermore, when looking at how `ChunkedStream.getMissingChunks` itself is implemented you'll notice that it (somewhat expectedly) always iterates over *all* chunks.
All in all, using `ChunkedStream.getMissingChunks` in the `ObjectLoader` seems like an unnecessary "heavy" and roundabout way to obtain a boolean value. However, it turns out there already exists a `ChunkedStream.allChunksLoaded` method, consisting of a *single* simple check, which seems like a perfect fit for the `ObjectLoader` use cases.
In particular, once the *entire* PDF document has been loaded (which is usually fairly quick with streaming enabled), you'd really want the `ObjectLoader` to be as simple/quick as possible (similar to e.g. loading a local files) which this patch should help with.
Note that I wouldn't expect this patch to have a huge effect on performance, but it will nonetheless save some CPU/memory resources when the `ObjectLoader` is used. (As usual this should help larger PDF documents, w.r.t. both file size and number of pages, the most.)
I completely overlooked this in PR 11281, but you obviously need to make similar changes in `PartialEvaluator.hasBlendModes` since it will otherwise ignore valid Blend Modes.
As can be seen in `PageViewport` only multiples of 90 degrees are really supported by the code, hence the unit-test doesn't really make sense.
(Possibly this should be enforced in the API, to avoid surprises, but given that this problem has always existed I'm passing on that for now.)
This argument is a left-over from older API code, where we unconditionally initialized `StatTimer` instances for every page. For quite some time that's only been done when `pdfBug` is set, hence it seems unnecessary to keep this functionality.
Even though the currect situation only results in six unnecessary function calls per page, it nonetheless seems completely unnecessary to call dummy functions when `pdfBug` is *not* set (i.e. the default behaviour).
For *very* long/large documents fetching all pages on load may cause quite bad performance, both memory and CPU wise. In order to at least slightly alleviate this, we can let the viewer treat these kind of documents[1] as if `disableAutoFetch` were set.
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[1] One example of a really bad case is https://bugzilla.mozilla.org/show_bug.cgi?id=1588435, which this patch should at least help somewhat. In general, for these cases, we'd probably need to implement switching between `PDFViewer`/`PDFSinglePageViewer` (as already tracked on GitHub) and use the latter for these kind of long documents.
Unfortunately I forgot to test `gulp mozcentraldiff` with PR 11256, which is really bad since it will cause the en-US `chrome.properties` l10n file to be deleted at mozilla-central; sorry about breaking this!
In order to address this we'll have to re-add (only) the en-US `chrome.properties` l10n file, which is simple enough. Furthermore, since we're not doing any sort of build-specific parsing of the l10n files, we can just copy the en-US files as-is rather than having to run `gulp locale` during `gulp mozcentral`.
As can be seen in the API, there's a number of document loading Exception handlers which are both really simple and highly similar. Hence these are changed such that all the relevant Exceptions are sent via *one* message instead.
Furthermore, the patch also avoids unnecessarily re-creating `UnknownErrorException`s at the worker side and removes an unnecessary `bind` call.
This was done automatically, using the `npm audit fix` command.
*Please note:* There's two vulnerabilities left, however they couldn't be fixed automatically and may thus benefit from being handled separately.
Obviously this won't look exactly right, but considering that the PDF file doesn't bother embedding non-standard fonts this is the best that we can do here.
Originally only `skipPages` existed, but given that `firstPage`/`lastPage` has existed for a long time now using them whenever possible looks simpler overall.
- In the `ibwa-bad` case the sixteenth page contains corrupt/incomplete commands, but given that we're suppressing `Error`s by default now skipping hardly seems warranted any more.
- In the `geothermal.pdf` case the first page contains an unsupported ColourSpace, but again we're suppressing `Error`s by default now and skipping hardly seems warranted any more.
With the removal of the (standalone) Firefox building code in PR 9566 (a year and a half ago), these files are now completely unused in the GitHub repository[1].
Hence it doesn't really seem necessary to keep fetching them with `gulp importl10n`, and the existing files in the `l10n` folder can also be removed (thanks to version control, they're easy enough to restore should the need ever arise).
The patch also allows an additional simplification, for the `gulp locale` and `gulp mozcentral` commands, since it's now possible to stop writing `l10n` files to the `extensions/firefox/` folder and instead just copy them similar to other build targets.
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[1] They're obviously still used in `mozilla-central`, for fallback messages displayed through `PdfStreamConverter.jsm`, but that doesn't make it necessary to keep them *here* as far as I'm concerned.
With the removal of the (standalone) Firefox building code in PR 9566 (a year and a half ago), these files are now completely unused.
Hence it doesn't really make sense to keep building them as part of `gulp locale`, and the existing files in the `l10n` folder can also be removed (thanks to version control, they're easy enough to restore should the need ever arise).
